138 NAOKI SUGITA 
appearance, that is, an ovoid form with a relatively large nucleus 
also ovoid or ellipsoid in form and a small amount of envelop; 
ing cytoplasm, which seems almost homogeneous in its staining, 
together with slender processes, until a brain weight of 0.75 gram. 
The Nissl bodies begin at first to appear in a brain weighing 0.9 
gram, as the ‘Kernkappe’ covering the apical part of the nucleus. 
The differentiation of the cytoplasm becomes more and more 
distinct as the brain weight increases and, in brains weighing 
more than 1.3 grams, the section as a whole takes a blue tone. 
This change in color tone is probably due to the development 
of the Nissl bodies in the cytoplasm and the structural changes 
in the intercellular tissue. The apical dendrites rapidly thicken in 
brains weighing 1.1 to 1.8 grams and, in brains weighing more 
than 1.3 grams, we see distinctly some relatively thick basal 
dendrites and the axis-cylinder becomes visible. The mass of 
the cytoplasm and the differentiation of the Nissl bodies proceeds 
steadily as the age advances. In the fully grown brain we see 
very often small satellite cells surrounding or indenting the 
cytoplasm of the ganglion cells, though satellite cells appear in 
relation to some other types of neurons also. Whatever the sig- 
nificance of these satellite cells, it is to be noted that in younger 
brains they are very rarely seen. The outline of the ganglion 
cell body is not necessarily sharp nor is the form regularly pyra- 
midal, being sometimes indeed quite irregular and often appear- 
ing ovoid or ellipsoid in shape. Lipochrome or fat pigment, 
usually seen in the adult human cells of this type, is never seen 
in those of the adult albino rat, even in old age. ; 
The nucleus of the young ganglior cell seems quite simple in 
structure and it attains nearly the full size in a brain weighing 
0.95 gram. After passing this stage, the chromatin structure 
of the nucleus begins to appear. ‘The size of the nucleus may be 
said to remain practically the same after this stage, while the 
cytoplasmic development continues relatively rapidly. The 
‘Kernfalte’ is sometimes visible in brains weighing more than 
1.5 grams. The nucleolus in the nucleus of the ganglion cells 
attains also nearly the full size (diameter is somewhat less 
than 4 micra) at the phase when the nucleus has reached nearly 
